﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using NPOI.SS.UserModel;
//using NPOI.XSSF.UserModel;
using NPOI.HSSF.UserModel;
using System.IO;
using System.Data;

public class ExcelHelper : IDisposable
{
    private string fileName = null; //文件名
    private HSSFWorkbook workbook = null;
    private FileStream fs = null;
    private bool disposed;

    public ExcelHelper(string fileName)
    {
        this.fileName = fileName;
        disposed = false;
    }

    /// <summary>
    /// 将DataTable数据导入到excel中
    /// </summary>
    /// <param name="data">要导入的数据</param>
    /// <param name="isColumnWritten">DataTable的列名是否要导入</param>
    /// <param name="sheetName">要导入的excel的sheet的名称</param>
    /// <returns>导入数据行数(包含列名那一行)</returns>
    public HSSFWorkbook DataTableToExcel(DataTable data, string sheetName, bool isColumnWritten, HSSFWorkbook sfworkbook = null)
    {
        int i = 0;
        int j = 0;
        int count = 0;
        ISheet sheet = null;

        if (File.Exists(fileName))
        {
            fs = File.OpenWrite(fileName);
        }
        else
        {
            fs = new FileStream(fileName, FileMode.Create, FileAccess.Write);
        }
        //if (fileName.IndexOf(".xlsx") > 0) // 2007版本
        //    workbook = new XSSFWorkbook();
        if (fileName.IndexOf(".xls") > 0) // 2003版本
        {
            if (sfworkbook == null)
            {
                workbook = new HSSFWorkbook();
            }
            else
            {
                workbook = sfworkbook;
            }
        }

        try
        {
            if (workbook != null)
            {
                sheet = workbook.CreateSheet(sheetName);
            }

            if (isColumnWritten == true) //写入DataTable的列名
            {
                IRow row = sheet.CreateRow(0);
                for (j = 0; j < data.Columns.Count; ++j)
                {
                    row.CreateCell(j).SetCellValue(data.Columns[j].ColumnName);
                }
                count = 1;
            }
            else
            {
                count = 0;
            }

            for (i = 0; i < data.Rows.Count; ++i)
            {
                IRow row = sheet.CreateRow(count);
                for (j = 0; j < data.Columns.Count; ++j)
                {
                    row.CreateCell(j).SetCellValue(data.Rows[i][j].ToString());
                }
                ++count;
            }
            workbook.Write(fs); //写入到excel
            fs.Close();
        }
        catch (Exception ex)
        {
            Console.WriteLine("Exception: " + ex.Message);
        }

        return workbook;
    }

    /// <summary>
    /// 将excel中的数据导入到DataTable中
    /// </summary>
    /// <param name="sheetName">excel工作薄sheet的名称</param>
    /// <param name="isFirstRowColumn">第一行是否是DataTable的列名</param>
    /// <returns>返回的DataTable</returns>
    public DataTable ExcelToDataTable(string sheetName, bool isFirstRowColumn)
    {
        ISheet sheet = null;
        DataTable data = new DataTable();
        int startRow = 0;
        try
        {
            fs = new FileStream(fileName, FileMode.Open, FileAccess.Read);
            //if (fileName.IndexOf(".xlsx") > 0) // 2007版本
            //    workbook = new XSSFWorkbook(fs);
            if (fileName.IndexOf(".xls") > 0) // 2003版本
                workbook = new HSSFWorkbook(fs);

            if (sheetName != null)
            {
                sheet = workbook.GetSheet(sheetName);
                if (sheet == null) //如果没有找到指定的sheetName对应的sheet，则尝试获取第一个sheet
                {
                    sheet = workbook.GetSheetAt(0);
                }
            }
            else
            {
                sheet = workbook.GetSheetAt(0);
            }
            if (sheet != null)
            {
                IRow firstRow = sheet.GetRow(0);
                int cellCount = firstRow.LastCellNum; //一行最后一个cell的编号 即总的列数

                if (isFirstRowColumn)
                {
                    for (int i = firstRow.FirstCellNum; i < cellCount; ++i)
                    {
                        ICell cell = firstRow.GetCell(i);
                        if (cell != null)
                        {
                            string cellValue = cell.StringCellValue;
                            if (cellValue != null)
                            {
                                DataColumn column = new DataColumn(cellValue);
                                data.Columns.Add(column);
                            }
                        }
                    }
                    startRow = sheet.FirstRowNum;
                }
                else
                {
                    startRow = sheet.FirstRowNum;
                }

                //最后一行的标号
                int rowCount = sheet.LastRowNum;
                for (int i = startRow; i <= rowCount; ++i)
                {
                    IRow row = sheet.GetRow(i);
                    if (row == null) 
                        continue; //没有数据的行默认是null　　　　　　　

                    DataRow dataRow = data.NewRow();
                    for (int j = row.FirstCellNum; j < cellCount; ++j)
                    {
                        if (row.GetCell(j) != null) //同理，没有数据的单元格都默认是null
                            dataRow[j] = row.GetCell(j).ToString();
                    }
                    data.Rows.Add(dataRow);
                }
            }

            return data;
        }
        catch (Exception ex)
        {
            Console.WriteLine("Exception: " + ex.Message);
            return null;
        }
    }

    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    protected virtual void Dispose(bool disposing)
    {
        if (!this.disposed)
        {
            if (disposing)
            {
                if (fs != null)
                    fs.Close();
            }

            fs = null;
            disposed = true;
        }
    }
}
